A widely used form of roadside vehicle barrier, commonly known as a crash barrier, consists of one or more, often two, steel rails of generally W cross-section supported by a line of posts and usually tensioned by inclined cables stayed by the end posts. Steel crash barriers have been known in the past to pierce into vehicles impacting the barriers end-on, with potentially horrific consequences for the occupants. To prevent such consequences, it is required by regulatory authorities in Australia that a prescribed initial number of posts at each end must be a specific and exact form of timber designed to snap in two when the barrier is subjected to vehicle impact greater than a predetermined severity. Snapping of the end posts allows the barrier to collapse away from rather than pierce the vehicle, while still absorbing its impact and slowing it down. The remaining intervening posts may be simple steel posts, eg of C-section channel.